News & Views
High-dose micronutrients promote skin health in European sea bass: study
By Ruby Gonzalez
Dosage of higher-than-recommended levels of micronutrients showed positive impact on skin health and fin erosions in European seabass, according to a new study.
“Fish during early life stages are quite susceptible to diseases and their immune system is not well-developed. Our goal was to understand if higher dose of these micronutrients could improve the health status of the fish,” Dr. Fotini Kokou told Hatchery International. She is one of the authors of the study, “Surplus of dietary micronutrients promotes antioxidant defense and improves fin erosions in European seabass (Dicentrarchus labrax) fry.”
Kokou and her team are from the Hellenic Center for Marine Research and University of Crete, both located in Greece; the Pontifical Catholic University of Valparaiso in Chile; and the Wageningen University and Research in the Netherlands.
In the control group, European seabass fry were fed with a diet including micronutrients zinc, niacin, selenium and ascorbic acid at recommended levels. The test group diet included surplus of these micronutrients. Based on the recommended levels, niacin was at 191 percent, selenium 236 percent, ascorbic acid 235 percent, and zinc 338 percent.
“Surplus of these micronutrients significantly reduced the percentage of fish with eroded fins, while also induced the activity of catalase and selenium-dependent glutathione peroxidase. Fish growth and bacterial loads in the water and fish skin mucus were not affected, whereas no skin lesions were observed,” the authors said.
In the Mediterranean, the main diseases related to the European seabass are mainly associated with bacteria, specifically Vibrio, Photobacterium and Tenacibaculum genera.
Kokou said, “Appearance of these diseases are associated with skin lesions (hemorrhages), while they also affect the intestine, spleen and muscles. Fin erosions are mainly associated with the high stocking densities when the fish are reared, and especially during these early stages.
“Stress can also cause fin erosions and skin wounds related to cages conditions, such as thunderstorm or bad weather conditions, or from predator attacks. In addition, the appearance of those symptoms can be related to different environments. For example, Tenacibaculum maritimum is more prevalent in lower temperatures and during winter compared to the other bacterial pathogens.”
Injuries from this bacterium, she continues, cause the most significant impact on fry health, causing high mortality rates and increased susceptibility to other pathogens.
Consequently, the bottom line is also affected. “High labor costs of treatment and enormous expenditures on chemotherapy have been reported and associated with this disease,” she said.